And the union hasn't seen OSHA using the "general duty clause" in federal occupational safety law — requiring safe workplaces - to restrict long hours on the job, said Lefton, who said some of his members are working 19 consecutive hours a day.

The agency disagrees.

"OSHA is very concerned about workplace fatigue and the effect it can have on workplace safety," it said in a statement. "We are prepared to cite employers when we discover situations in which the health and safety of workers is put at risk because of long work hours."

After the BP refinery explosion in 2005 that killed 15 workers in Texas City, the union met with industry representatives to establish standards on work hours.

But the union broke off from the negotiations with the American Petroleum Institute, contending the discussions - which eventually resulted in a recommended practices standard - didn't address fatigue.

Lefton pushed unsuccessfully for a requirement that employees get a 48-hour break after putting in four consecutive 12-hour days.

But it's cheaper for the petrochemical industry to put an employee on required overtime at time-and-a-half pay than to hire replacements for employees who quit or retire, he said.

The American Petroleum Institute said in a prepared statement that the industry is implementing elements of the fatigue standard, but it didn't have details.

Under the new agreement, employees who work three consecutive 16-hour days must receive a 24-hour break. Employees on regular shifts must get a 48-hour break if they work 21 days in a row.

"The purpose of the policy is to provide reasonable assurance that the safety and health of employees, co-workers, facilities and the community are not adversely affected because of fatigue caused by excessive work hours," Dow representative Tracie Copeland said. A similar policy for its facility in Texas City will be discussed during upcoming negotiations, Copeland added.

Airline industry standards

In the airline industry, rules on the number of hours that pilots and other airline employees can work haven't changed much since 1985, said Capt. Mike Hynes, a pilot who serves on the safety committee with the Air Line Pilots Association in Houston. During that time, planes and flight times have gotten faster, and fewer pilots are in the cockpit.

Regulations haven't kept up, Hynes said, so union contracts have evolved faster than federal rules on the issue of fatigue.

One of the hurdles is the industry's good safety record - only one fatal airline crash in the United States in four years - and a resulting perception that existing rules are adequate.

Regulators have to do a cost-benefit analysis when proposing new regulations. It's fairly easy to calculate the cost of reducing individual work hours, such as the need for more employees, but the benefits are harder to quantify.

"How do we justify the added expense?" Hynes said.

Continental pilots can call in and report they're too fatigued to fly, said Jocelyn LaBove, director/counsel for labor relations for Continental Airlines, a subsidiary of United Continental Holdings. But she said that doesn't happen often, which suggests to her that it's not a big problem.

Some of the responsibility to stay rested, she said, lies with individual employees, whether fatigue results from a late night of partying or a long commute.